1.2.6: Patch release

This patch release fixes a bug introduced in 1.2.5 and other minor issues.

Added

• The AppImage version does now provide all drumkits in /usr/share/hydrogen/data/drumkits/ and /usr/local/share/hydrogen/data/drumkits/ via the "Sound Library" as session kits.

Changed

• Sample loading in songs has been made more portable.

Fixed

• Fix velocity automation for patterns that are not of size 4/4 (#2171).
• Fix saving and loading of sample files introduced in 1.2.5 (#2174).